1. Field of the Invention
The present invention generally relates to the measurement of transient friction at the head-disk interface during spin up of a disk file and, more particularly, to a tunable electro-mechanical or piezoelectric transducer in a servo feedback loop which allows accurate measurement of transient friction.
2. Description of the Prior Art
Accurate characterization of transient friction at the head-disk interface during spin up of a disk file is essential for proper design of lubricated overcoats on recording media, the spindle motor and other associated components of a magnetic disk drive for a computer storage device. Normally, the transient friction is measured using strain gauges which deform proportionally to the transient friction at the head-disk interface. Because of the deformation of the strain gauge, the first measurement is reduced, thus limiting the accuracy with which the friction may be measured. Hatamura et al. in "A Measurement of Sliding Resistance Forces for Various Heads and Disks by High-Rigid Force Sensor", IEEE Trans. on Maqnetics, Vol. 24, No. 6, Nov. 1988, pp.2638-2640, describe their observations that the force cannot be measured accurately because the present force sensors are so soft that large deformation in measuring disturbs the head assembly. Furthermore, discrepancies between friction data obtained using different strain gauge arrangements has also been found.